Fluid pressure actuator

ABSTRACT

The actuator comprises a clutch pedal lever (12) which is pivotally connected to a support (17). The pedal is integral with a cylinder (18) having a piston (20) therein which is connected to a hollow pushrod (28). The pushrod is also pivotally connected to the mounting (17). Pivoting movement of the pedal (12) causes the cylinder (18) to move relative to the piston so that fluid within the cylinder will operate a slave cylinder (44). The clutch and pushrod have spaced axes of pivoting (13a, 14a) and the piston (20) is shaped to permit a degree of tilting to take place between the piston and the cylinder. The system also includes a reservoir which can communicate with the cylinder when the piston occupies a particular position in the cylinder.

The invention relates to a fluid pressure actuator and is particularly,but not exclusively concerned with a fluid pressure actuator forcontrolling the clutch or brakes of a vehicle.

Hitherto, it has been commonplace to use a pedal in a vehicle whichapplies pressure and displacement to a pushrod arranged to operate apiston contained within a separate hydraulic master cylinder assembly.The pressure is then transmitted through a hydraulic line to operate ahydraulic slave cylinder for operating, e.g., a clutch of the vehicle.

It has been proposed hitherto to provide a pedal having a cylinderthereon for operating a remote slave cylinder. Examples of such pedalsare described in WO87/03344 and EP-A-0293082.

In WO87/003344, it is necessary to provide a camming arrangement whichcauses a piston to move into the cylinder during pivoting movement ofthe pedal. In EP-A-0293082 it is necessary for the cylinder to bepivotally mounted on the pedal and for an operating rod of the piston tobe pivotally mounted to a bracket on the vehicle bulkhead.

An object of the present invention is to provide an improved actuatorwhich, in particular, avoids the need for a camming device.

According to the invention there is provided a fluid pressure actuatorcomprising a cylinder rigid with a lever to be mounted for pivotingabout an axis, the piston being axially slidable in said cylinder, thepiston having an operating member extending therefrom to be mounted at aposition remote from the piston for pivoting about a further axis spacedfrom the axis of pivoting of the lever, the operating member beingarranged to tilt relative to the cylinder during pivotal movement of thelever.

With there being one pivotal mounting for the lever and one pivotalmounting for the operating member, an additional pivot as inEP-A-0293982 is not required and it is unnecessary to provide a camingarrangement as described in WO87/03344.

The tilting of the operating member relative to the cylinder can beaccommodated by appropriate shaping of the piston. For example, thepiston may be tapered from a position adjacent one end to enable it totilt within the cylinder or it may alternatively be barrel-shaped. Suchan arrangement provides a simple and convenient way of accommodating thetilting movement of the piston and is particularly advantageous in thatrespect.

The operating member may be a tubular rod through which fluid from theactuator passes to operate a device such as a slave cylinder. Thetubular rod may be connected to or may be integral with a hollowmounting through which fluid passes. The axis of pivoting of the tubularrod may, in such a case, be an axis of pivoting for the hollow mounting.The hollow mounting may include passage means for communication with areservoir. The reservoir may be of a remotely located type connected tothe hollow mounting by means of a suitable conduit.

The operating member may be associated with a valve which enables thecylinder to communicate with a reservoir when the piston occupies agiven position within the cylinder. The valve may comprise a sealassociated with the operating member which may be arranged to permit orprevent communication with the reservoir. The seal may be an annularseal arranged to engage a surface surrounding an orifice leading to,e.g., the slave cylinder.

The operating member may be axially rigid with the piston and movementof the cylinder towards a rest position may permit the operating memberto cause the valve to permit communication with the reservoir. Movementof the piston away from the rest position may then cause the valve toengage the surface around the orifice to inhibit communication betweenthe cylinder and the reservoir.

The valve may be at an end of the operating member adjacent the piston.

In another embodiment the operating member may be axially movablerelative to the piston and movement of the piston towards a restposition may, in that case, cause the operating member to operate thevalve so as to permit communication with the reservoir.

The reservoir may be provided on the cylinder and may be defined withina gaiter or the like mounted on one end of the cylinder. In such a case,fluid from the reservoir may be arranged to communicate with thecylinder when the piston is at a given position within the cylinder byflowing through slots in the operating member.

Stop means may be provided for retaining the piston in the cylinder.

Spring means may be provided for biasing the piston towards one end ofthe cylinder, the spring preferably being arranged to bias the pistontowards the stop means.

Movement of the cylinder towards its rest position preferably causes thestop means to move the piston axially thereby operating the valve topermit communication with the reservoir.

As mentioned above, the operating rod is preferably hollow and providesa very convenient duct along which the fluid can pass from the cylinderto operate a device. The hollow operating member also provides aconvenient means of enabling fluid to pass between the reservoir and thecylinder when the piston occupies a given position in the cylinder.

Normally, the valve will close to inhibit flow of fluid between thereservoir and the cylinder at the onset of pivoting of the lever tooperate the external device such as the slave cylinder.

A fluid pressure actuator in accordance with the invention will now bedescribed by way of example with reference to the accompanying drawingsin which:

FIG. 1 is an elevation of an actuator in accordance with the inventionshown partly in cross-section,

FIG. 1A is a view similar to FIG. 1 showing the actuator in a pivotedposition.

FIG. 2 is a perspective view of the actuator shown in FIG. 1illustrating connections to a reservoir and slave cylinder,

FIG. 3 is a cross-section through a piston and cylinder of the actuatorillustrating a valve arrangement controlling flow of fluid from thereservoir,

FIG. 4 is a perspective view of an alternative type of actuator having asealed reservoir,

FIG. 5 is a cross-section through a cylinder of the actuator of FIG. 4illustrating a valve arrangement for controlling flow of fluid betweenthe cylinder and the reservoir,

FIG. 6 is a cross-section through a two-part connector for use inconnecting the actuator shown in FIGS. 4 and 5 to a slave cylinder, theconnector parts being shown disconnected,

FIG. 7 is a view of the connector parts shown in FIG. 6 in a connectedcondition,

FIG. 8 is a cross-section through part of a cylinder of an actuator inaccordance with the invention showing another type of piston, and

FIG. 9 is a view similar to FIG. 8 illustrating a further type ofpiston.

Referring to FIGS. 1-3, an actuator indicated generally at 10 comprisesa clutch pedal lever 12 having a boss 13 housing a shaft 14. The shaft14 is pivotally mounted in coaxial apertures 15 formed in parallelflanges 16 of a bulkhead mounting bracket 17 and defines an axis ofpivoting 14a. The bracket 17 can be suitably secured to a bulkhead orfirewall (not shown) of a vehicle. The pedal 12 is moulded from plasticsmaterial so as to form an integral cylinder 18. The cylinder 18 definesa cylindrical bore 19 in which a piston 20 is slidably located. Thepiston is shown in detail in FIG. 3 and comprises an annular pistonmember 22 having an external peripheral groove 23 in which a seal 24 islocated. The seal 24 sealingly engages the wall of bore 19. The pistonmember 22 is formed with a through bore 25 which includes a counterbore26 and a reduced diameter bore 27. The counterbore 26 forms a shoulder26a on the piston member 22. A hollow pushrod 28 fits into the pistonmember 22 and has a reduced diameter portion 29 located within thereduced diameter bore 27. A shoulder 28a is defined between the mainsection of the pushrod and the reduced diameter section 27. The lowerend of the pushrod 28 as viewed in the drawings is bent outwardly at 30with shoulders 26a, 28a in interengagement so as to secure the pistonmember 22 to the piston rod 28. The piston member 22 is formed with areduced diameter section 32 so as to define a shoulder 33. A spring 34extends between a lower end wall 35 of the cylinder 18 and the shoulder33. Four bores 34 extend between a bore 28a of the pushrod 28 and theshoulders 33. The spring 34 normally urges the piston member 22 againsta snap-ring 36 in a groove 37 in the cylinder. The snap-ring 36 forms astop for the piston 20.

The upper end of the pushrod 28 is housed within a valve unit 38 whichis pivotally mounted in apertures 39 in the flanges 16 of mountingbracket 17 for pivoting about an axis 38a. The pushrod 28 has anenlarged head 40 located in a bore 42 which communicates via an orifice41 with a passageway 43 leading to a slave cylinder 44 and communicatesthrough a further passageway 45 with a reservoir 46. The pushrod 28 isretained in the bore 42 by means of a screw-threaded retainer 46 whichscrews into a screw-threaded section 47 of the bore 42. The retainer 46is formed with a groove 48 which houses a seal 49 sealingly engaging thepushrod 28. The upper end of the head 40 has an annular groove 50therein which houses a seal 52. The seal 52 acts as a valve and isengageable with an annular face 53 of the valve unit which surrounds theorifice 41.

The passage 43 communicates with the slave cylinder 44 through flexibleconduit 54 which may be secured to the valve unit 38 by means of ascrew-threaded retainer 55. The communication with the reservoir 46 islikewise through conduit 56 which is push-fitted onto an extension 57 onthe valve unit 38.

In use, the cylinder 18, pushrod 28, valve unit 38, conduit 54, 56 andslave cylinder 44 are filled with hydraulic fluid and bled of any air.In that condition, the piston and cylinder will normally occupy a restposition as shown in FIG. 3. To operate the slave cylinder, a force F(FIG. 1A) is applied to a foot-engaging pad 58 so as to pivot the pedal12 about the axis 14a thereby causing the cylinder 18 to move upwardly.The initial upward movement of the cylinder enables the piston 20 tomove upwardly under the influence of spring 34 until the seal 52 engagesthe annular surface 53 around orifice 41 thereby preventingcommunication between a lower chamber 18a of the cylinder 18 and thereservoir 46. Further upward movement of the cylinder 18 then causesfluid to move from chamber 18a through pushrod bore 28a directly and viabores 34, the fluid passing through passageway 43 and conduit 54 tooperate the slave cylinder 44. On removing the load F, the clutch pedal12 pivots in a reverse sense under the influence of a clutch operated byslave cylinder 44, the spring 34 and a clutch lever return spring 59connected between the clutch pedal 12 and an arm 59a on the bracket 17.

The axis of pivoting 38a of valve unit 38 and the axis of pivoting 14aof the pedal 12 are spaced apart and, therefore, the pivotal movement ofthe pedal 12 will cause the pushrod 28 to tilt slightly relative to thecylinder 18 as seen in FIG. 1A. Such tilting is accomodated by formingthe piston member 22 so as to define a clearance 60 between the bore 19of cylinder 18 and the periphery of the piston member 22 and by formingthe piston member 22 with spherical upper and lower sections 22a, 22b.In that way, the piston 20 and pushrod 28 can tilt relative to thecylinder.

To prevent ingress of foreign matter into the cylinder 18, a flexibleseal 62 is mounted on the cylinder and slidably engages the pushrod 28.

FIGS. 4 and 5 show an alternative actuator where the reservoir ismounted on the piston. Parts in FIGS. 4 and 5 which generally correspondto parts shown in FIGS. 1-3 carry the same reference numerals and willnot be described in detail.

In FIGS. 4 and 5, the piston 20 includes an alternative form of pistonmember 70 having a peripheral groove 72 which houses a seal 73 insealing engagement with the bore 19 of cylinder 18. A hollow piston rod28 is integral with a mounting 75 at its upper end having stub shafts 76thereon pivotally mounted in the side plates 16 of bracket 17. The upperend of the pushrod 28 has an extension 77 secured to conduit 54.

The lower end of the pushrod 28 is formed with a head 78 which isretained slidably within a bore 79 of the piston member 70 by means of asnap-ring 80. The snap-ring 80 locates in a groove 82 formed in thepiston member 70. The piston member 70 has an end wall 83 formed with athrough bore 84. The end wall 83 of the piston engages a return spring34 which extends between the end wall 33 and an end face 35 of thecylinder 18. The piston member 70 has an external groove 85 to which aflexible gaiter 86 is snap fitted. The gaiter 86 has an inner end 87which grips the pushrod 28 to define a reservoir 88 for fluid.

The end wall 83 of the piston member 72 is formed with an annular groove89 which houses a seal 90 which co-operates with the head 78 to act as avalve.

The head 78 of the pushrod 28 is formed with a plurality of axial slots91.

The flexible conduit 54 may be connected to the slave cylinder 44 eitherdirectly or via a self sealing connector 92 described below.

The cylinder 18 is provided with a snap-ring 36 as in FIGS. 1-3 againstwhich the piston member 70 is normally urged by means of the spring 34.

In use, the system is filled with hydraulic fluid bled of air asdescribed with reference to FIGS. 1-3. When the clutch pedal 12 ispivoted under the influence of force F, the cylinder 18 initially movesupwardly relative to the pushrod 28 thereby causing the lower surface ofhead 78 to sealingly engage the seal 90. In that way, communicationbetween a lower chamber 18a of the cylinder and the reservoir 86 isprevented. Further upward movement of the cylinder 18 causes end wall 35to move towards the piston 70 and fluid is thereby forced from chamber18a through the pushrod 28 to the slave cylinder 44.

When the force F is removed, the clutch pedal 12 returns to its restposition under the influence of the clutch released by the slavecylinder 44, the spring 34 and the clutch lever return spring 59. As thecylinder 18 moves towards its FIG. 5 position, the head 78 of the pistonrod 28 will eventually disengage the seal 90 to permit communicationbetween the reservoir 88 and the fluid in the chamber 18a of cylinder 18via the grooves 91 and the bore 84. The gaiter 86 will expand orcollapse as the volume of hydraulic fluid contained within it changes.

As with the arrangement shown in FIGS. 1-3, the spacing of the pivotalaxis 14a, 38a will cause the pushrod 74 to tilt relative to the cylinder18 during upward and downward movement of the cylinder. That can againbe accommodated by providing a clearance 60 between the piston member 70and the bore 19 and by forming the piston member 70 with spherical upperand lower sections 70a, 70b.

The arrangement shown in FIGS. 4 and 5 lends itself particularly to apre-filled and pre-bled system. To ease assembly into a vehicle in sucha case, the self sealing connector 92 may be provided to connectportions 54a and 54b of the conduit 54.

The connector 92 comprises a male part 95 and a female part 96. The malepart comprises an annular leading section 97 having a bevelled leadingedge 98 and defining a bore 99. The leading section 97 supports a seal100 which sealingly engages a valve member 102. The valve member 102 iscup-shaped and defines radial ports 103 adjacent a shoulder 104. Thevalve 102 defines an internal shoulder 105 which locates a spring 106extending between the shoulder 105 and an end wall 107 of the malemember. The spring 106 normally urges the shoulder 104 of the valvemember 102 against a shoulder 108 on the leading section 197. The malemember has an external shoulder 109 thereon and also has a tubularprojection 124 for a conduit part 54a leading to the actuator.

The female member 96 includes a body 110 formed with a plurality ofleading latch-fingers 111 formed with bevel lead-in surfaces 112. Thebody 110 has a cylindrical bore 110a therein in which an annular sealmember 114 is slidably mounted. The annular seal member 114 has an innersurface 115 having spaced-apart 116 seals thereon in sealing engagementwith a cylindrical projection 117 formed with an axial bore 118 and aradial port 119 between the two seals 116 and in communication with bore118. The seal member 114 is normally urged into engagement with latchsurfaces 120 on the fingers 111 by means of a spring 122 acting betweenan end face 123 of the female coupling 96 and the seal member 114. Atubular projection 125 is provided for a conduit part 54b leading to theslave cylinder 44.

To interconnect the male and female parts 95, 96 the male part 95 isintroduced into the female part 96 so that the leading surfaces 98 ofthe male part initially engage lead-in surfaces 112 of the fingers 111.Continued movement of the parts 95, 96 towards each other causes theprojection 117 to push the valve member 102 to the right and causes thefingers 112 to ride over the male section 95 until they eventually snapbehind the shoulder 109 as shown in FIG. 7. Simultaneously, the malemember pushes the seal member 114 to the left until the valve member 102and seal member 114 take up the FIG. 7 position. In that position, fluidcan flow through bore 101 in the male part 95 through ports 103, throughport 119 in the female part and through bore 118 as shown by arrows inFIG. 7.

The interconnection between the male and female connector parts 95, 96establishes a hydraulic link between the conduit parts 54a, 54b withminimal loss of fluid or introduction of air into the system.

FIGS. 8 and 9 illustrate alternative shapes for the pistons.

In FIG. 8, the piston 20 is substantially barrel-shaped to permittilting of the piston within the cylinder bore 19. The piston is formedwith a suitably shaped groove 126 for a seal 127 which sealingly engagesthe wall 19. The barrel-shape provides tapering clearances 130, 132which permit sufficient degree of tilting of the piston and pushrodabout the seal relative to the cylinder 18.

In FIG. 9, the seal 127 is located adjacent one end of the piston 20 andthe piston member tapers towards its upper end providing a taperingclearance 133. The clearance 133 permits a degree of tilting about theseal 127.

In all of the embodiments described with reference to the accompanyingdrawings, tilting of the piston does not affect the sealing engagementbetween the seal on the piston and the wall of the cylinder.

The cylinder 18 may have a metal cylinder liner press fitted or mouldedtherein to reduce wear, friction or porosity.

Although in FIG. 1 the hydraulic fluid passes through a hollow pushrod28, the fluid could be tapped from a port in the wall of the cylinder18.

The reservoir allows topping up with hydraulic fluid for displacement orwear compensation and/or bleeding of the system to remove air.

In FIG. 2, the reservoir 46 may be sealed by a flexible diaphragm andsuch a system may lend itself to being pre-filled for shipping andinstallation. Alternatively, the reservoir may be open to the ambientair.

The actuator may be used to operate brakes instead of a clutch. Inanother application, the lever may be a hand operated lever instead of aclutch or brake pedal.

I claim:
 1. A hydraulic master cylinder comprising a lever to be mountedat one end for pivoting about a pivot axis, the other end being anoperating end of the lever, a cylinder rigid with the lever and having ablind bore, the open end of said bore being adjacent the pivot axis, andthe base of the bore being adjacent the operating end of the lever, apiston axially slidable in said cylinder, the piston having an operatingmember extending out of the open end of the bore, the operating memberbeing mountable at a position remote from the piston for pivoting abouta further pivot axis spaced from the axis of pivoting of the lever, andthe operating member being generally coaxial of the bore and beingarranged to tilt relative to the cylinder during pivotal movement of thelever.
 2. An actuator according to claim 1 in which the piston isarranged to tilt relative to the cylinder during pivotal movement of thelever.
 3. An actuator according to claim 2 in which the piston is shapedto permit relative tilting between the piston and cylinder.
 4. Anactuator according to claim 3 in which the piston has a taperingconfiguration.
 5. An actuator according to claim 3 in which the pistonhas a barrel-like configuration.
 6. An actuator according to claim 1 inwhich the operating member is a tubular rod through which fluid from theactuator passes to operate a device.
 7. An actuator according to claim 6in which the tubular rod is connected to or integral with a hollowmounting through which fluid passes, the mounting being pivotal topermit pivotal movement of the tubular rod.
 8. An actuator according toclaim 7 in which the hollow mounting includes passage means forcommunication with a reservoir.
 9. An actuator according to claim 1 inwhich the operating member is associated with a valve which enables thecylinder to communicate with a reservoir.
 10. An actuator according toclaim 9 in which the valve comprises a seal associated with theoperating member which is arranged to permit or prevent communicationbetween the cylinder and the reservoir.
 11. An actuator according toclaim 10 in which the seal is at an end of the operating member remotefrom the piston.
 12. An actuator according to claim 11 in which theoperating member is axially rigid with said piston and movement of thecylinder towards a rest position permits the operating member to causethe valve to permit communication with the reservoir.
 13. An actuatoraccording to claim 10 in which the valve is at an end of the operatingmember adjacent the piston.
 14. An actuator according to claim 13 inwhich the operating member is axially movable relative to the piston andmovement of the cylinder towards a rest position causes the operatingmember to operate the valve so as to permit communication with thereservoir.
 15. An actuator according to claim 9 in which the reservoiris remotely located and communicates with the cylinder through conduit.16. An actuator according to claim 9 in which the reservoir is providedon the cylinder.
 17. An actuator according to claim 16 in which thereservoir is defined within a gaiter mounted on one end of the cylinder.18. An actuator according to claim 17 in which the operating memberpasses coaxially through the reservoir.
 19. An actuator according toclaim 1 in which stop means is provided for retaining the piston in thecylinder.
 20. An actuator according to claim 19 in which spring means isprovided for biasing the piston normally towards the stop means.
 21. Anactuator according to claim 19 in which movement of the cylinder towardsits rest position causes the stop means to move the piston axiallythereby operating the valve to permit communication with the reservoir.22. An actuator according to claim 1 in which the lever and cylinder areformed as a one piece unit.